One of the things that I've seen DDL triggers used for is a sanity check on dropped tables... It's one the more popular examples of DDL triggers I've seen in the MS documentation...

CREATE TRIGGER no_drop

ON DATABASE

FOR DROP_TABLE

AS

PRINT 'Tables cannot be dropped!'

ROLLBACK;

The above will keep everyone from dropping tables. You'd need to modify it to allow only certain users to drop the table, and/or just disable it when you need to drop something and then re-enable it when you are done...

-Luke.